Hair treatment method

ABSTRACT

A hand held device generates a predetermined number of pulses of light having a predetermined electromagnetic spectrum, a predetermined duration, a predetermined inter-pulse interval, and a predetermined total energy. The pulse sequence is delivered to a skin surface to temporarily remove hair. A period of time for reappearance of hair on the selected skin surface after the using of the device to remove hair from the selected skin surface is determined by counting the days to hair reappearance after a test light application. Subsequently, the device is used periodically to apply the pulses of light to the selected skin surface at intervals of shorter length than the determined period of hair regeneration, thereby temporarily maintaining the selected skin surface free of visible hair.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of application No.10/291,086 filed Nov. 8, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to a hair treatment process.More particularly, this invention relates to a method for the temporaryremoval of hair and for the retardation of hair growth.

[0003] As discussed in U.S. Pat. No. 6,280,438, hair may be removed fromselected skin surfaces by the application of intense, wide area, pulsedelectromagnetic (light) energy. According to the methodology of U.S.Pat. No. 6,280,438, the energy heats the hair and coagulates the tissuearound the hair and follicle without damaging the healthy skin. Pursuantto that prior art disclosure, it is preferable to provide an opticallytransparent water based gel on the skin prior to treatment with theelectromagnetic energy. The gel cools the epidermis but is applied so asnot to enter the cavity around the hair follicle, and thus does not coolthe hair and the hair follicle. The applied energy then coagulates thehair without damaging the skin.

[0004] U.S. Pat. No. 6,280,438 teaches the use of incoherentpolychromatic radiation in a wavelength range that penetrates into theskin without being highly attenuated. It is indicated in the patent thatwavelengths shorter than 550 nm are not useful because they will behighly attenuated before reaching the lower parts of the hair follicles.Instead, wavelengths in the range of 550 to 630 nm are heavily absorbedby blood and can therefore be used to coagulate the vessels that feedthe hairs. Additionally, longer wavelengths, in the range of 600 to 1100nm have a very good penetration into non-pigmented skin and can be usedto couple to the melanin of the hair.

[0005] U.S. Pat. No. 5,885,273 discloses a method of removing hair thatincludes producing a plurality of pulses of incoherent electromagneticenergy, which is filtered in accordance with the color of the hair beingremoved. A flashlamp produces pulses having delays on the order of 0.1msec to 100 msec, and an energy fluence on the order of 10 to 100 J/cm².Energy that has a wavelength of less than 500 nm or 600 nm and greaterthan 1300 nm is preferably filtered out. Light is applied to the treatedarea in either a long pulse or in a sequence of pulses separated by adelay. The delay and/or pulse length is preferably controlled by theoperator to provide enough heat to remove the hair but not enough heatto damage the skin. For example, the pulse length or delay between thepulses should be more than the cooling time of the gel covered epidermisand less than the cooling time of the hair and follicle. Specifically, apulse length of 50 msec if a single pulse is used or a delay of 50 msecbetween the pulses if a pulse sequence is used are appropriate values.

[0006] In brief, the art using electromagnetic radiation such as pulsesof incoherent light is intended to permanently remove hair from selectedskin surfaces. The light pulses have parameters such as spectraldispersion, pulse duration and total energy that are selected to destroythe hair follicles in the selected skin area. Understandably, suchmethods carry a certain amount of risk that the skin may be damaged.Accordingly, the prior art methods of hair depilation are typicallyintended for use by trained cosmetologists and other professionals. Theconsuming public is left with few options in removing undesired hair.

OBJECTS OF THE INVENTION

[0007] An object of the present invention is to provide a method fortreating hair to at least retard hair growth.

[0008] It is a related object of the present invention to provide amethod for temporary hair removal.

[0009] A more particular object of the present invention is to providesuch a method of hair treatment or removal that is safe for home use.

[0010] It is a related object of the invention to provide a method forhair treatment, which may replace current home-based methods, forinstance, of shaving, waxing, plucking, tweezing, or using depilatories.

[0011] A further object of the present invention is to provide such atreatment method that can result in a smooth cleaner hair removal thanis possible with razors and shavers.

[0012] These and other objects of the present invention will be apparentfrom the drawings and descriptions herein. It is to be understood thateach object of the invention is achieved by at least one embodiment ofthe invention. It is not necessarily the case that any embodimentachieves all of the objects of the invention.

SUMMARY OF THE INVENTION

[0013] A hair treatment method comprises, in accordance with the presentinvention, generating a predetermined number of pulses of light eachhaving a predetermined electromagnetic spectrum, and directing thepulses of light towards a skin surface. The light pulses having at leastone pulse duration, at least one inter-pulse interval (if the number ofpulses is greater than one), and a total energy all predetermined to atleast temporarily retard growth of hair along the skin surface. Afterlapse of a period of time after the directing of the pulses towards theskin surface, the predetermined number of pulses of light are againgenerated and directed towards the skin surface.

[0014] The pulse parameters, namely, the pulse number, the pulseduration(s), the inter-pulse interval(s), the total energy and thespectral distribution(s), are selected in concert to only retard thegrowth of hair and/or to temporarily prevent the appearance of hair onthe treated skin surface. Thus, in contrast to prior methods, which areaimed at completely destroying the hair follicle and terminating hairgrowth, the present method contemplates only a partial destruction ofthe follicles or, alternatively, a destruction of the hair inside thefollicles. In either case, the hair will grow and again appear on thetreated surface in the absence of additional controlled lightapplication. However, the rate at which the hair grows will be reducedby virtue of the application of electromagnetic radiation pursuant tothe present invention.

[0015] The light used in a hair treatment method in accordance with thepresent invention may be incoherent and produced by a flashlamp or othersource of incoherent electromagnetic radiation. Alternatively, the lightmay be coherent and produced by a laser source. In the former case theelectromagnetic spectrum of the light pulses is a band of wavelengths,while in the latter case, the electromagnetic spectrum of a light pulsedelivered at one time is a single wavelength. In the former case filtersmay be used to limit the band of transmitted wavelengths, while in thelatter case the laser source may be adjustable or tunable for producingwavelengths of different frequencies.

[0016] In accordance with the present invention, a user determines thetime it takes for the hair to regenerate and reappear on the treatedskin surface and reapplies the light pulses prior to the expected timeof hair growth through the treated skin surface. Owing to a hair growthrate that may decrease with continuing application of light energy, theuser need reapply the light pulses at an increasing interval. Morespecifically, a hair removal method in accordance with the presentinvention includes generating a predetermined number of pulses of lighteach having a predetermined electromagnetic spectrum and applying thepulses of light to a given skin surface, the pulses having at least onepredetermined pulse duration, at least one predetermined inter-pulseinterval (if the number of pulses is greater than one), and apredetermined total energy. The various pulse parameters are“predetermined” insofar as they are set or selected prior to theapplication of the light energy to the selected skin surface. Thedetermination of the different pulse parameters is generally madepartially at the time of manufacture of the light-generating device andpartially by the selection or selections made by the user. At least inpart owing to the application of the pulses to the skin surface, anappearance of visible hair fibers on the skin surface is temporarilyprevented. Passing days are then counted between the applying of thepulses to the skin surface and a subsequent reappearance of hair fiberson the skin surface, thereby determining an expected hair regenerationperiod. After determination of this hair regeneration period, the samepulse sequence is generated, having the same pulse number, the sameelectromagnetic spectrum(s), the same pulse duration(s), the sameinter-pulse interval(s) (if applicable), and the same total energy. Thispulse sequence is directed towards the given skin surface. Thereafter,prior to a lapse of the determined hair regeneration period, the lightapplication is repeated with pulses of light having (if desired) thesame spectrum, the same number, the same duration, the same inter-pulseinterval (if applicable), and the same total energy. It is to be notedthat the hair regeneration period may lengthen with time, in part as aresult of the light treatments. In recognition of that potentiality, theregeneration time may be recalculated after any given number oftreatments. And if the regeneration time does increase, the intervalbetween successive light treatments may be increased accordingly.

[0017] The present invention is thus directed to a method for thetemporary removal of hair wherein light application is repeated prior tohair reappearance. This method serves to maintain a smooth and hair freeskin surface continuously as long as the light application is repeatedin due course prior to the expected time of hair reappearance.

[0018] The method of the present invention contemplates a gradualreduction in the frequency of light treatment, owing to a diminution inthe hair growth rate. In an example, a user may initially be required toapply the pulsed light energy at intervals of one week in order toprevent the reappearance of hair on the treated hair surface. Afterseveral weeks or months of periodic light treatment, this rate of lightenergy application may be reduced to biweekly or monthly applications.The initial period of hair reappearance, as well as the rate of hairgrowth retardation, will be determined by the individual's genetics asto skin color, hair color, hair thickness, hair density, etc., and bythe selected treatment parameters such as total energy, pulse rate,pulse duration, light spectrum, etc., as well as by the particular areaon the user's body. In any given individual, the growth rates of hair onthe face, underarms, legs, etc., vary. In addition, the change in hairgrowth rate using the present methodology may differ from body area tobody area. The light treatment method of the present invention alsoaffects hair parameters other than growth rate. Again depending on theindividual's genetics, the location of the hair treated, and theselected treatment parameters, the user's hair may experience changes inthickness, density, and color. More specifically, in many individuals,hair is likely to become finer, less dense, and lighter in color.

[0019] The method of the present invention may be applied to facialhair, leg hair, underarm hair, chest hair, etc., using hand held devicesof prior art designs, for instance, with a light source such as aflashlamp, a reflector, one or more lenses, and an application interfacesuch as a skin-contacting crystal. The crystal may function as a coolingelement. Alternatively, a separate cooling medium such as a gel may beapplied to the skin surface prior to the light application.

[0020] Accordingly, the present invention contemplates the use of a handheld device for generating a predetermined number of pulses of lighthaving a predetermined electromagnetic spectrum and for applying thepulses of light to a skin surface, the pulses having one or morepredetermined durations, one or more predetermined inter-pulse intervals(if number of pulses is greater than one), and a predetermined totalenergy. The device is used to temporarily remove hair from a selectedskin surface and will in many cases retard the rate of hair growth. Aperiod of time for reappearance of hair on the selected skin surfaceafter the using of the device to remove hair from the selected skinsurface is determined, for instance, by simply counting the days to hairreappearance after a test light application. Subsequently, the device isused periodically to apply the pulses of light to the selected skinsurface at intervals of shorter length than the determined period ofhair regeneration, thereby temporarily maintaining the selected skinsurface free of visible hair. The regeneration time after any number oftreatments may be measured again after any number of light treatmentsessions. If the regeneration time is increased (owning to hair growthretardation), the interval between successive light treatments may beincreased accordingly.

[0021] The inter-pulse interval (where the number of pulses is greaterthan one) may, in different applications of the invention, be anywherefrom 1 millisecond to 2 seconds. Generally, the smaller the inter-pulseinterval, the greater the risk of damage to the skin. Thus, the smallerinter-pulse intervals should be used only in professional settings. Inhome-based embodiments of the invention, the inter-pulse interval of alight treatment is preferably greater than 200 msec. An inter-pulseinterval of such a magnitude allows partial cooling of the hairfollicles and reduces the chances of complete follicle destruction andinadvertent damage to the epidermis. Preferably, the inter-pulseinterval is between 200 msec and about 500 msec. An inter-pulse intervalof 300 msec is effective.

[0022] The total energy applied may be anywhere from 1 Joule per squarecentimeter of treated skin surface to about 200 J/cm². Generally, thehigher energies entail greater risk to skin integrity and should be usedonly by skilled professionals. For home use, the total energy appliedshould be lower, between approximately 5 J/cm² and approximately 40J/cm² of the skin surface. This energy range is appropriate for personsof light skin color. Where the skin color is on the dark side, the upperlimit of the total energy applied to a unit of skin surface should beless, for instance, approximately 20 J/cm².

[0023] Generally, it is contemplated that devices used in a methodpursuant to the present invention will require a selection of a maximumor total energy to be applied to a skin surface. This requirementtypically entails some restriction on the user's freedom in selectingthe magnitudes of other pulse parameters. In a simple device, the usermay be able to select only one pulse parameter, namely the total energy.Such a device might, for instance, have high, medium and low settings.In a more complex device, setting of the total energy applied by a pulsesequence will limit the range of options available to the user insetting the other parameters. For instance, once the user selects thetotal energy and the pulse duration, the number of pulses is determined,provided that the rate of energy production or intensity is notadjustable. If the intensity is adjustable, the user will have someleeway in selecting both the pulse duration and the number of pulses. Inthat case, the intensity may be automatically controlled by thelight-generating device so that the total energy does not exceed the setvalue.

[0024] The duration of the light bursts or pulses may be as little as 1millisecond or as great as two seconds. The shortest durations andhigher energies are recommended for professionally supervised lighttreatments only. For ordinary consumers or unskilled users, the pulseduration should be longer, preferably above approximately 6 msec andmore preferably between approximately 6 msec and approximately 20 msec.A pulse duration of 7 msec is effective.

[0025] Pursuant to one embodiment of the present invention, the light ofthe pulses is incoherent and the spectrum includes wavelengths betweenabout 300 nm and 1200 nm. Longer wavelengths are used for darker skin,for deeper hairs and deeper removal. In some embodiments of theinvention, the spectrum of the pulses may be limited to wavelengthsbetween about 300 nm and 550 nm. These embodiments will require a morefrequent application of the light energy to effectuate temporary hairremoval. However, because of the retardation of hair growth, thefrequency of light application required to maintain a hair free skinsurface will generally decrease with use.

[0026] The number of pulses in each pulse sequence or treatment session(as applied to a given skin area) may be between one and ten, while thetotal duration of a pulse sequence ranges between 1 millisecond and 38seconds.

[0027] As indicated above, the present invention contemplates that someadjustment may be made by the user in the particular operationalparameters of the light application device. For instance, a simplehand-held device may have a plurality of settings, for instance, high,medium, and low, where one or more of the operational parameters havedifferent pre-established values depending on the setting. Thus, high,medium, and low settings may vary in the number of applied pulses, thepulse duration, the inter-pulse interval, and/or the total energyapplied. A user could start with a low setting to see whether the hairfalls out and if not, try the next higher setting. Usually, it ispreferable to use the lowest setting which accomplishes the desiredresult.

[0028] It is to be noted that consumer devices may be preprogrammed withautomatically operating safety controls which inhibit the user frominadvertently exposing himself or herself to dangerous quantities oflight energy. Thus, in a relatively complex consumer product, the user'ssetting of one parameter at a potentially dangerous value will cause thedevice either to limit the selectable ranges of one or more other pulseparameters or to automatically adjust pulse parameters to prevent anexcessive rate of energy delivery. For instance, the selection of asmall inter-pulse interval may prevent the user from selecting a longpulse duration and/or a small number of pulses or, alternatively, mayresult in an automatic diminution of the intensity (e.g., via engagementof an intensity-reducing filter).

[0029] The present invention provides a method for the temporary removalof hair. The method is safe for home use. The energies used aresufficiently low to avoid skin damage. Because the light is appliedprior to the appearance of hair on a skin surface, the skin surface maybe maintained in a hairless condition continuously. If the individualwishes to grow hair at any location, this is possible by merelyrefraining from light application. The present invention contemplatesthe use of a light applicator periodically, say, at intervals of a weekto a few months. In some cases, the light application may be daily, as asubstitute for daily shaving with a razor or shaver.

[0030] In contrast to shaving, which cuts hairs at or above the skinsurface, the method of present invention severs the hairs below the skinsurface, thereby presenting a smoother, cleaner, more complete hairremoval. In contrast, all conventional methods of hair removal,including shaving, waxing, plucking, tweezing, electrolysis, laser lightapplication, incoherent light application, or the use of depilatories,require the protrusion of the hairs at the skin surface.

[0031] It should be understood that the present methodology may be usedin professional settings, in spas or salons, by professional cosmeticservice providers. Higher energies may be used in such settings. Evenhigher energies and more complex settings may be used by licensedmedical professionals in medical offices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a block diagram of a light-pulse generating device foruse in a method in accordance with the present invention.

[0033]FIG. 2 is a block diagram of another light-pulse generating devicefor use in a method in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] As depicted in FIG. 1, a device for generating light pulses forapplication to a skin surface in a hair treatment process includes amanually operable setting selector 10 connected at an output to a memory12 in turn connected at an output to a control unit 14. Memory 12 storespre-established combinations of light pulse parameters including pulsewidth or duration, inter-pulse interval or delay time, pulse number,light intensity, and total treatment energy. Control unit 14 may be amicroprocessor or a special logic circuit connected to a pulse generator16 for inducing the generator to produce a sequence of electricalcontrol pulses fed to a source 18 of incoherent light energy. Source 18produces light with a spectral distribution including wavelengthsbetween 500 nm and 1200 nm. Control unit 14 may be connected directly tosource 18 where the source incorporates means for varying pulseparameters pursuant to encoded instructions.

[0035] Light source 18 (as well as the entire light pulse applicator)may take any known form such as those disclosed in U.S. Pat. No.6,280,438 and U.S. Pat. No. 5,885,273. Thus, light source 18 may be aXenon flashlamp.

[0036] Light 20 generated by source 18 is directed through an array ofoptical elements 22 that may include one or more reflectors, lenses, andfilters (not separately shown). Where an ad justable filter is included,control unit 14 may be connected to the filter for operatively modifyingthe action thereof. For instance, in the case of an adjustable neutraldensity filter, control unit 14 may induce a change in the filterdensity to control the intensity, and therefore the power, of the lightapplied to a selected skin surface.

[0037] In the case of multiple wavelengths of light being produced, anadjustable filter may be included in the optical elements 22 and/or theapplicator interface 26. These filters can block undesired wavelengthsand allow desired wavelengths to pass. Low end filters that block loweror shorter wavelengths, high end filters that block higher or longerwavelengths or band pass filters that block some high or some low endwavelengths may be utilized.

[0038] Light 24 leaving the optical array 22 is delivered or applied toa skin surface via an applicator or interface element 26 exemplarilytaking the form of a crystal. U.S. Pat. No. 6,280,438 and U.S. Pat. No.5,885,273 disclose kinds of applicators or interfaces utilizable in thedevice of FIG. 1 (or 2). Applicator or interface element 26 may functionin part to cool the skin surface prior to, during, and/or after a lightapplication procedure. Cooling may be accomplished by using acrystal-type applicator or interface 26, with or without a layer of gel,as described in U.S. Pat. No. 6,280,438 and U.S. Pat. No. 5,885,273.

[0039] The elements of FIG. 1 are encased in or mounted to a housing 28of a size and configuration enabling the pulse generation device to behand held and easily manipulated for purposes of optically treatingdifferent skin surfaces of the individual user.

[0040] The device of FIG. 1 is preprogrammed to produce light pulses inany of several settings, each setting being defined by a respectivecombination of particular operational parameters including pulseduration, inter-pulse interval, pulse number, and intensity or totalenergy. For instance, the device may have a plurality of settings, forinstance, high, medium, and low, which vary in the number of appliedpulses (e.g., 3, 2, 1), the pulse duration (9 msec, 7 msec, 5 msec), theinter-pulse interval (250 msec, 300 msec, 350 msec), and/or the totalenergy applied (35 J/cm², 20 J/cm², 10 J/cm²). A user could start with alow setting to see whether the hair falls out and if not, try the nexthigher setting. Usually, it is preferable to use the lowest settingwhich accomplishes the desired result.

[0041] A more advanced or complex device is illustrated in FIG. 2. Thisdevice includes a housing 30 having manually actuatable input elements32, 34, 36, and 38, such as rotary knobs or a solid-state touch screen,which enable a user to individually select multiple operatingparameters. Input elements or selectors 32, 34, 36, and 28 are aninter-pulse interval selector, a pulse number selector, a power orenergy selector, and a pulse duration selection, respectively. Anotherselector (not shown) could be for intensity adjustment, while a furtherselector may be provided for adjusting a light source 42 or a filter inoptical elements 48 and/or an applicator 52 for modifying the wavelengthband delivered to the target skin surface. Selectors 32, 34, 36, and 38are operatively tied to a control unit 40 such as a microprocessor orhard-wired log circuit. Control unit 40 regulates the operation of lightsource 42 such as a conventional flashlamp, either directly orindirectly via a pulse generator 44. Light 46 from source 42 istransmitted along a path through optical elements 48 optionallyincluding one or more reflectors, lenses, and filters (not separatelyshown). Light 50 at an output of the optical array 48 is applied to askin surface via applicator or interface element 52. Applicator orinterface element 52 may take the form of a crystal block or atransparent or translucent pouch filled with a transparent ortranslucent fluid such as a gel or a liquid. In the case of a gel, thepouch (52) may be provided with perforations on a skin-contactingsurface for exuding the gel of cooling purposes. Alternatively, as shownin FIG. 2, the light pulse device may be provided with a fluid dispensersuch as a spray nozzle 54 connected to a valve 56 downstream of apressurized coolant reservoir 58. In response to an operation of amanual actuator 60 or in response to signals from control unit 40, valve56 enables a flow of coolant from reservoir 58 to nozzle 54 forapplication to a selected skin surface. In the event that applicator orinterface element 52 is a bag or pouch, reservoir 58 and valve 56 may beconnected to the applicator or interface element for supplying a gel orfluid coolant thereto.

[0042] In one embodiment of the device of FIG. 2, suitable forprofessional but not home use, inter-pulse interval selector 32 providesfor intervals in a range from 1 msec and 2 seconds, whereas pulse numberselector 34 is enabled for pulse sequences of one to ten pulses. Inaddition, power selector 36 permits treatment energies between 1 Jouleper square centimeter of skin surface and 200 Joules per squarecentimeter, while pulse duration selector 38 enables pulses of 1 msec to2 seconds in length. Total pulse sequence duration, from the beginningof the first pulse to the termination of the final pulse, ranges from 1msec to 38 seconds. The various pulse sequence parameters may beselectable from sets of discrete values or, alternatively, fromcontinuous ranges.

[0043] In the device of FIG. 2, the various parameters are typically notcompletely independent inasmuch as the total energy selected willfunction as a constraint on the ranges available for the otherparameters, that is, the total energy selected will serve to regulate orcircumscribe the ranges available to the user for the other pulsesequence parameters. Where the device of FIG. 2 has no intensityadjustment capability, a selection of the total energy and the pulseduration may determine the number of pulses. Similarly, a selection ofthe total energy and the number of pulses may determine the pulseduration. If the intensity is an adjustable parameter, once the totalenergy has been chosen, the user will be able to select the magnitudesof two of the three parameters, pulse duration, intensity and number ofpulses. The inter-pulse interval is related to the rate at which radiantenergy is applied to a skin surface and may accordingly be subjected tosome programmed control. Longer pulse durations and/or delays willdeliver energy at a slower rate (total energy is distributed over longertime) and therefore be safer to use with higher energy levels.Preferably, the total energy is always a selectable parameter and isbest selected prior to the setting of the other parameters. However, thedevice of FIG. 2 may be preprogrammed to limit the rate at which radiantenergy is applied to a skin surface, which will force restrictions onthe user's ability to select pulse parameter values.

[0044] In an alternative embodiment of the device of FIG. 2, suitablefor home use, inter-pulse interval selector 32 enables a selection ofintervals ranging from 200 msec to 2 seconds, while power selector 36enables treatment energies between 1 J/cm² and 40 J/cm². Preferably, thepulse duration and the number of pulses available for selection arerestricted so as to prevent the user from delivering energy at too higha rate. If the user selects a large pulse number, the pulse duration isnecessarily short, whereas a small number of pulses forces a longerpulse duration in order to achieve the selected total energy. It ispreferable to use a larger number of pulses and a smaller pulse durationin order to limit the rate at which light energy is applied to a skinsurface. Pulse number selector 34 may therefore enable a selection ofthree to ten pulses per pulse sequence, while pulse duration selector 38enables a selection of pulses lasting 1 msec to 10 msec. The variouspulse sequence parameters may be selectable from sets of discrete valuesor, alternatively, from continuous ranges.

[0045] A person uses the device of FIG. 1 or 2 to apply pulses of lightto a skin surface for purposes of effectively severing or destroyinghair fibers below the surface of the skin to temporarily prevent hairsfrom growing through and thus becoming visible on the skin. The userfirst performs a calibration or initialization procedure to determine anappropriate pulse setting and a hair-regeneration period for thatsetting. The term “hair-regeneration period” is used herein to denotethe time it takes for hair to reappear on the skin surface after a pulsesequence has been applied to that surface at a selected setting.

[0046] During the calibration or initialization stage, the user shouldfirst select a low-energy pulse sequence to determine whether thatsequence is effective in removing the hair of a selected skin region.The individual may find that a given setting does not adequately removethe hair (e.g., some hairs do not fall out) or requires a too frequenttreatment. In such cases, the individual should retry the calibration orinitialization procedure using a higher-energy setting.

[0047] Using the device of FIG. 1, an individual will first select a lowsetting to determine whether that low setting is effective in hairremoval. If not, a next higher or medium setting may be tried.Generally, higher settings will be used only as the circumstanceswarrant, for instance, if the hair fibers are thick and the skin islight.

[0048] In determining optimal settings with the device of FIG. 2, a usershould choose initial parameter values which in combination result inthe application of small amounts of energy. Thus, where one or moreselected pulse parameters are associated with high treatment energies,other pulse parameters should be selected that are associated with lowtreatment energies.

[0049] Where all the pulse parameters are independently adjustable,lower treatment energies will generally result from settings involvingfew pulses (say, 1-3 instead of 8-10 pulses), long inter-pulse intervals(300 msec or more), short pulse durations (20 msec or less), low lightintensity (if selectable, for example, via an adjustable neutral densityfilter), and low total energies (less than 40 Joules per squarecentimeter of skin surface). If a given setting proves to beineffective, the user might adjust selector 32 or 38 to decrease theinter-pulse interval or increase the pulse length, thereby effectivelyincreasing the power or rate at which the radiant energy is delivered tothe target skin surface. Alternatively or additionally, the user mightincrease the number of pulses via selector 34 or increase the appliedenergy via selector 36. These adjustments will result in an increase inthe rate of applied energy if the total time of the pulse sequence islimited. If the light intensity is separately adjustable, one mayincrease the power or rate of energy delivery by simply selecting ahigher intensity value.

[0050] Where the various pulse parameters are not independentlyselectable, for instance, where the total energy applied is acontrolling factor, adjustments made in the parameters for purposes ofincrementally enhancing the hair removal effectiveness of the device ofFIG. 2 will be different from the case of completely independentparameter values. For instance, once the total applied energy and totalpulse sequence time have been selected, decreasing the number of pulseswill require an increase in pulse length and/or an increase in pulseintensity in order to deliver the same amount of total energy in thefixed time. These changes will increase the effectiveness of the lightapplication inasmuch as the rate of energy delivery is increased. Incontrast, once the total applied energy and total pulse sequence timehave been selected, increasing the pulse duration will decrease theinstantaneous rate at which energy is applied to the target skin surfaceby decreasing the light intensity,.

[0051] During the calibration or initialization stage of a hair removalmethod using the device of FIG. 1 or FIG. 2, light is used on skinsurfaces with visible and protruding hair. Light is applied to the skinsurface and the hair and is directed downward towards the base or bulbof the hair. Immediate damage to the hair may be noted but is notessential. Hairs may fall out during the course of the following month.Hair loss may be gradual or abrupt. No assistance is usually needed inthis process.

[0052] Since hair growth rates vary from person to person and fordifferent body locations on the same person, each user should note theinterval between the first treatment and the reappearance of new hair oneach skin area.

[0053] Because different skin areas have different grades of hair(different colors, different fiber diameters, different hair densities)and different skin pigmentation, etc., different pulse parametersettings are recommended for different skin areas. For example,different settings will be necessary for the underarms and the legs inorder to optimize results. In addition, depilation schedules may alsovary from one skin area to another.

[0054] After the user has determined appropriate settings of the pulsesequence parameters and expected hair-regeneration periods for differentskin areas, the user then treats each skin surface with pulsed light atthe respective setting and at a periodicity set by the respectivehair-regeneration period. Successive applications of pulsed light followat intervals smaller than the detected hair-regeneration period. Forinstance, if it is determined that hair reappears on a leg at threeweeks after treatment with light at a given pulse sequence setting, thenlight energy at that setting is applied to the leg at, say, two weekintervals to maintain the leg free of visible hair. The regenerationperiod may be measured again after any number of treatments. And if theuser finds that the regeneration time has changed, the interval betweensuccessive treatment sessions may be adjusted accordingly.

[0055] This hair removal method contemplates, therefore, the periodicapplication to a selected skin surface of a pulse sequence having apredetermined number of pulses of light of a predeterminedelectromagnetic spectrum, a predetermined duration, a predeterminedinter-pulse interval, and a predetermined total energy. These pulsesequence parameters are determined in part by the design of the lightgenerating device used and in part by the selections made by the user.The light treatment temporarily prevents a growth of hair through theselected skin surface for the respective hair-regeneration period.

[0056] The light of the pulses is generally incoherent and the spectrumincludes wavelengths between about 300 nm and 1200 nm. However, singlewavelengths of laser or coherent light may be delivered at one time,when desired. Higher wavelengths are used for darker skin, for deeperhairs and deeper removal. In order to limit the depth of penetration ofthe light, and accordingly the length of the hair-regeneration orhair-regrowth period, the spectrum of the pulses may be limited toshorter wavelengths and may include wavelengths, for instance, below 550nm.

[0057] In other embodiments of a light generation and applicationdevice, one or more of the pulse parameters may vary during a singletreatment session. For instance, the inter-pulse interval or the pulseduration may increase or decrease from the beginning of a pulse sequenceto the end of the pulse sequence. The resulting instantaneous rate ofenergy application may therefore vary during the pulse sequence.

[0058] Listed below are a number of exemplary settings or combinationsof operational parameters particularly suitable for home-use andattainable with either the device of FIG. 1 having pre-establishedsettings or parameter combinations or the device of FIG. 2 where thevarious pulse sequence parameters may be individually adjustedindependently of the other parameters. In these examples, the totaltimes of the pulse sequences are determined by the selected numbers ofpulses, the selected pulse durations and the selected inter-pulseintervals. The light intensity may be automatically adjusted by thelight generating device if necessary to ensure consistency among thelisted parameter settings.

[0059] Home Use Example 1. In a preferred setting or combination ofoperational parameters suitable for home use, an incoherent lightapplicator device for temporary hair removal generates pulses with apulse number of two, a pulse duration of 7 msec, an inter-pulse intervalof 300 msec, a total pulse energy of 20 J/cm², and a spectraldistribution of a commercially available flashlamp, includingwavelengths between 500 and 1200 nm.

[0060] Home Use Example 2. A slightly higher setting or combination ofoperational parameters for an incoherent light applicator devicesuitable for home use involves a pulse sequence with a pulse number oftwo, a pulse duration of 7 msec, an inter-pulse interval of 250 msec, atotal pulse energy of 20 J/cm², and a spectral distribution of acommercially available flashlamp, including wavelengths between 500 and1200 nm. Although the total amount of energy is the same as in the firstexample, the shorter interpulse interval means that the rate of energytransmission to the target skin surface is higher.

[0061] Home Use Example 3. A higher setting or combination ofoperational parameters for an incoherent light applicator deviceinvolves pulses with a pulse number of two, a pulse duration of 5 msec,an inter-pulse interval of 250 msec, a total pulse energy of 25 J/cm²,and a spectral distribution of a commercially available flashlamp,including wavelengths between 500 and 1200 nm. In this example, not onlyis the total energy larger than in the second example, but the rate ofenergy application is higher owing to the shorter pulse duration.

[0062] Home Use Example 4. An even higher setting or combination ofoperational parameters for an incoherent light applicator deviceinvolves pulses with a pulse number of two, a pulse duration of 5 msec,an inter-pulse interval of 210 msec, a total pulse energy of 37 J/cm²,and a spectral distribution of a commercially available flashlamp,including wavelengths between 500 and 1200 nm. The pulse sequence ofthis example delivers radiant energy at a higher rate than in the thirdexample because of the shorter inter-pulse interval and the slightlyhigher energy delivered per pulse.

[0063] Home Use Example 5. In a low setting or combination ofoperational parameters, an incoherent light applicator device producespulses with a pulse number of two, a pulse duration of 5 msec, aninter-pulse interval of 350 msec, a total pulse energy of 15 J/cm², anda spectral distribution of a commercially available flashlamp, includingwavelengths between 500 and 1200 nm. The pulse sequence of this exampledelivers a small amount of energy, at a low rate (e.g., long inter-pulseinterval).

[0064] Home Use Example 6. A slightly higher setting or combination ofoperational parameters for an incoherent light applicator deviceinvolves pulses with a pulse number of two, a pulse duration of 5 msec,an inter-pulse interval of 300 msec, a total pulse energy of 20 J/cm²,and a spectral distribution of a commercially available flashlamp,including wavelengths between 500 and 1200 nm.

[0065] Home Use Example 7. A lower setting or combination of operationalparameters for an incoherent light applicator device involves pulseswith a pulse number of three, a pulse duration of 5 msec, an inter-pulseinterval of 300 msec, a total pulse energy of 20 J/cm², and a spectraldistribution of a commercially available flashlamp, includingwavelengths between 500 and 1200 nm.

[0066] Home Use Example 8. Another setting or combination of operationalparameters for an incoherent light applicator device involves pulseswith a pulse number of two, a pulse duration of 7 msec, an inter-pulseinterval of 250 msec, a total pulse energy of 20 J/cm², and a spectraldistribution of a commercially available flashlamp, includingwavelengths between 500 and 1200 nm.

[0067] The devices of FIGS. 1 and 2 may be provided with a band-passfilter for limiting the spectral distribution of the generated lightpulses to wavelengths in a given band, for instance, between 700 nm and900 nm. Alternatively, a low-pass filter may be used for transmitting toa skin surface only wavelengths less than a predetermined maximum, suchas 900 nm, 750 nm, or 550 nm. The lower the wavelength the less likelythe light will penetrate deeply and damage cellular and histologicalelements as deep as the bulb parts of the hair follicles. Shorterwavelengths, for instance, below 550 nm are useful for limiting thedepth of penetration. It is to be understood, however, that the less thedepth of penetration, the shorter the time between successiveapplications of light energy necessary to maintain a hair free skinsurface. Thus, instead of a month or a week, the time between successivehair removal procedures might be as little as one or two days.

[0068] Depth of penetration may also be limited by using lower lightintensities. Neutral density or “gray” filters may be used to reduce theintensity of the light applied to the selected skin surfaces.

[0069] Listed below are a number of exemplary settings or combinationsof operational parameters particularly suitable for professionaldevices. In these examples, the total times of the pulse sequences aredetermined by the selected numbers of pulses, the selected pulsedurations and the selected inter-pulse intervals. The light intensitymay be automatically adjusted by the light generating device ifnecessary to ensure consistency among the listed parameter settings.

[0070] Professional Use Example 1. In a setting or combination ofoperational parameters suitable for professional use, an incoherentlight applicator device for temporary hair removal generates pulses witha pulse number of two, a pulse duration of 7 msec, an inter-pulseinterval of 150 msec, a total pulse energy of 60 J/cm², and a spectraldistribution of a commercially available flashlamp, includingwavelengths between 500 and 1200 nm.

[0071] Professional Use Example 2. A slightly higher setting orcombination of operational parameters for an incoherent light applicatordevice involves pulses with a pulse number of two, a pulse duration of 7msec, an inter-pulse interval of 100 msec, a total pulse energy of 60J/cm², and a spectral distribution of a commercially availableflashlamp, including wavelengths between 500 and 1200 nm.

[0072] Professional Use Example 3. A lower setting or combination ofoperational parameters for an incoherent light applicator deviceinvolves pulses with a pulse number of two, a pulse duration of 9 msec,an inter-pulse interval of 100 msec, a total pulse energy of 60 J/cm²,and a spectral distribution of a commercially available flashlamp,including wavelengths between 500 and 1200 nm.

[0073] Professional Use Example 4. A higher setting or combination ofoperational parameters for an incoherent light applicator deviceinvolves pulses with a pulse number of two, a pulse duration of 9 msec,an inter-pulse interval of 100 msec, a total pulse energy of 100 J/cm²,and a spectral distribution of a commercially available flashlamp,including wavelengths between 500 and 1200 nm.

[0074] Professional Use Example 5. In a relatively low setting orcombination of operational parameters for professional use, anincoherent light applicator device produces pulses with a pulse numberof two, a pulse duration of 9 msec, an inter-pulse interval of 200 msec,a total pulse energy of 40 J/cm², and a spectral distribution of acommercially available flashlamp, including wavelengths between 500 and1200 nm.

[0075] Professional Use Example 6. A slightly higher setting orcombination of operational parameters for an incoherent light applicatordevice involves pulses with a pulse number of two, a pulse duration of 5msec, an inter-pulse interval of 150 msec, a total pulse energy of 40J/cm², and a spectral distribution of a commercially availableflashlamp, including wavelengths between 500 and 1200 nm.

[0076] Professional Use Example 7. Another higher setting or combinationof operational parameters for an incoherent light applicator deviceinvolves pulses with a pulse number of two, a pulse duration of 5 msec,an inter-pulse interval of 150 msec, a total pulse energy of 50 J/cm²,and a spectral distribution of a commercially available flashlamp,including wavelengths between 500 and 1200 nm.

[0077] An incoherent light applicator device for professional use mayalso be provided with a band-pass filter for limiting the spectraldistribution of the generated light pulses to wavelengths in a givenband, for instance, between 700 nm and 900 nm. Again, a low-pass filtermay be used for transmitting to a skin surface only wavelengths lessthan a predetermined maximum, such as 900 nm, 750 nm, or 550 nm.

[0078] The hair treatment method described above with reference to FIGS.1 and 2 results not only in a temporary hair removal at an opticallytreated skin surface, but also retards the growth of hair fibers locatedat or along that skin surface. By counting the days to hair reappearanceafter several hair depilation procedures over a course of a few months,it is possible to determine a reduction in hair growth rate owing to theapplication of electromagnetic radiation. A user who starts using thelight application process at one inter-application interval maysubsequently use a longer inter-application interval and still maintaina hair-free skin surface. Of course, the degree of hair growth ratereduction will vary from person to person and even from skin location toskin location on the same person. For example, two users initiallyrequired to apply the pulsed light energy at intervals of one week inorder to prevent the reappearance of hair on the treated hair surfacemay find that after several months one user need reapply light energyonly every two weeks and the other user need reapply light energy onlyevery month.

[0079] It is to be noted that the hair treatment method described hereincontemplates multiple passes over any particular skin surface. Theselected light treatment parameters may be the same for each pass or mayvary from pass to pass. In addition, the passes may follow immediatelyafter one another or may be spaced by an interval during which, forinstance, the light treatment device is used to apply light pulses toanother area of the user's skin. An advantage of multiple passes is thatthe total power applied to a given skin surface may be reduced relativeto that needed for accomplishing the desired hair removal by a singlepass or light treatment. For example, instead of a single pass of 50Joules/cm², hair could be effectively removed temporarily by two passesof 20 Joules/cm² apiece.

[0080] Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. For example, light sources 18 and 42 may take theform of laser sources. In that case, if optical elements 22 and 48include any filters, those filters are neutral density filters forreducing the intensity of the transmitted radiation. Where light sources18 and 42 are tunable laser sources, then an additional actuator may beprovided for frequency selection purposes. Accordingly, it is to beunderstood that the drawings and descriptions herein are proffered byway of example to facilitate comprehension of the invention and shouldnot be construed to limit the scope thereof.

What is claimed:
 1. A hair treatment method comprising: generating apredetermined number of pulses of light each having a predeterminedelectromagnetic spectrum; directing said pulses of light towards a skinsurface, said pulses having at least one pulse duration, and a totalenergy all predetermined to at least temporarily retard growth of hairalong said skin surface; and after lapse of a period of time after thedirecting of said pulses towards said skin surface, again generatingsaid predetermined number of pulses of light and directing the pulsestowards said skin surface.
 2. The method defined in claim 1 wherein saidnumber of pulses is greater than one, said pulses having an inter-pulseinterval greater than 200 msec.
 3. The method defined in claim 2 whereinsaid total energy is between approximately 1 Joule and approximately 200Joules of energy per square centimeter of said skin surface.
 4. Themethod defined in claim 3 wherein said duration is between approximately1 msec and approximately 2 seconds.
 5. The method defined in claim 4wherein the light of said pulses is incoherent and wherein said spectrumincludes wavelengths between about 300 nm and 1200 nm.
 6. The methoddefined in claim 5 wherein said spectrum includes only wavelengthsbetween about 300 nm and about 550 nm.
 7. The method defined in claim 4wherein said duration is between approximately 1 msec and approximately20 msec.
 8. The method defined in claim 3 wherein said total energy isbetween approximately 5 Joules and approximately 40 Joules of energy persquare centimeter of said skin surface.
 9. The method defined in claim 1wherein said period of time has a length between a day and nine months.10. A hair treatment method comprising: generating a predeterminednumber of pulses of light each having a predetermined electromagneticspectrum; applying said pulses of light to a skin surface, said pulseshaving at least one predetermined pulse duration, and a predeterminedtotal energy; at least in part owing to the applying of said pulses tosaid skin surface, temporarily preventing an appearance of hair fiberson said skin surface; counting days between the applying of said pulsesto said skin surface and a subsequent reappearance of hair fibers onsaid skin surface to determine a first lapsed period of time; afterdetermining of said period of time, generating additional pulses oflight of said predetermined number and having said spectrum; directingsaid additional pulses of light towards said skin surface, saidadditional pulses having said duration, and said total energy; countingdays between the directing of said additional pulses towards said skinsurface and a subsequent reappearance of hair fibers on said skinsurface to determine a second lapsed period of time longer than saidfirst lapsed period of time; after determining of said period of time,generating supplemental pulses of light of said predetermined number andhaving said spectrum; directing said supplemental pulses of lighttowards said skin surface, said supplemental pulses having saidduration, and said total energy; prior to a lapse of said second lapsedperiod of time after the directing of said supplemental pulses towardssaid skin surface, generating further pulses of light of saidpredetermined number and having said spectrum; and directing saidfurther pulses of light towards said skin surface, said further pulseshaving said duration, and said total energy.
 11. The method defined inclaim 10 wherein said number of pulses is greater than one, said pulseshaving an inter-pulse interval between 1 msec and 2 seconds.
 12. Themethod defined in claim 11 wherein said inter-pulse interval is greaterthan 200 msec.
 13. The method defined in claim 10 wherein said totalenergy is between approximately 1 Joule and approximately 200 Joules ofenergy per square centimeter of said skin surface.
 14. The methoddefined in claim 10 wherein said duration is between approximately 1msec and approximately 2 seconds.
 15. The method defined in claim 10wherein the light of said pulses is incoherent and wherein said spectrumincludes wavelengths between about 300 nm and 1200 nm.
 16. The methoddefined in claim 15 wherein said spectrum includes wavelengths betweenabout 300 nm and about 550 nm only.
 17. The method defined in claim 10wherein said second lapsed period of time has a length between a day andnine months.
 18. A hair removal method comprising: providing a hand helddevice for generating a predetermined number of pulses of light eachhaving a predetermined electromagnetic spectrum and for applying saidpulses of light to a skin surface, said pulses having at least onepredetermined pulse duration, and a predetermined total energy; andusing said device to temporarily remove hair from a selected skinsurface.
 19. The method defined in claim 18 wherein said number ofpulses is greater than one, said pulses having an inter-pulse intervalbetween 1 msec and 2 seconds.
 20. The method defined in claim 19 whereinsaid inter-pulse interval is greater than 200 msec.
 21. The methoddefined in claim 18 wherein said total energy is between approximately 1Joule and approximately 200 Joules of energy per square centimeter ofsaid skin surface.
 22. The method defined in claim 18 wherein saidduration is between approximately 1 msec and approximately 2 seconds.23. The method defined in claim 18 wherein the light of said pulses isincoherent and wherein said spectrum includes wavelengths between about300 nm and 550 nm only.
 24. The method defined in claim 18, furthercomprising: determining a period of time for reappearance of hair onsaid selected skin surface after the using of said device to remove hairfrom said selected skin surface; and subsequently periodically usingsaid device to apply said pulses of light to said selected skin surfaceat intervals of shorter length than said period of time, therebytemporarily maintaining said selected skin surface free of visible hair.25. A hair treatment method comprising: providing a hand held device forgenerating a predetermined number of pulses of light each having apredetermined electromagnetic spectrum and for applying said pulses oflight to a skin surface, said pulses having at least one predeterminedpulse duration, and a predetermined total energy; and using said deviceto at least temporarily retard hair growth along a selected skinsurface.
 26. The method defined in claim 25, further comprisingsubsequently periodically using said device to apply said pulses oflight to said selected skin surface at intervals of increasing lengthowing to a diminution in a growth rate of hair along said skin surface.27. The method defined in claim 26 wherein said number of pulses isgreater than one, said pulses having an inter-pulse interval between 1msec and 2 seconds.
 28. The method defined in claim 26 wherein saidtotal energy is between approximately 1 Joule and approximately 200Joules of energy per square centimeter of said skin surface.
 29. Themethod defined in claim 28 wherein said duration is betweenapproximately 1 msec and approximately 2 seconds.
 30. The method definedin claim 29 wherein the light of said pulses is incoherent and whereinsaid spectrum includes wavelengths between about 300 nm and 550 nm only.